This invention relates generally to cannulas adapted for both oral and nasal applications for monitoring breathing of a patient, sampling the end tidal CO2 content in the exhaled breath of a patient to determine the patient's CO2 blood concentration level, or supplying a treating gas, such as oxygen, to a patient. In addition, the invention relates to a method of manufacturing a cannula adapted to interconnect with both nasal passages and the mouth for use to monitor breathing, sample end tidal CO2, supplying a treating gas and is especially suitably for the detection of apnea (the absence of breathing).
Nasal cannulas are commonly used to administer a treating gas, such as oxygen, to humans having respiratory problems. Illustrations of nasal cannulas used for this purpose are found in U.S. Pat. No. 3,802,431. Nasal cannulas have been used also for inhalation therapy, made possible by development of inhalation sensors such as described in U.S. Pat. No. 4,745,925. A nasal cannula can be used to monitor breathing and for detection of apnea when connected to an inhalation sensor.
Nasal cannulas additionally adapted to communicate with the mouth of a patient to permit administration of a gas or sensing of apnea during periods of mouth breathing or nasal blockage are also known.
The present invention relates to a novel cannula and method of manufacturing a cannula having the ability to communicate with both nasal cavities as well as the mouth or oral cavity of a patient. This method provides, in the preferred embodiment, disconnectable mandrels which, when assembled, form a mold over which a cannula forming polymeric material is applied, and which, through the capability of each mandrel component being disconnectable from the other component(s), facilitates removal of the mandrels from the formed or manufactured cannula.
Prior art relating to dipping of a part in a plastisol to create a coating is exemplified by U.S. Pat. Nos. 3,906,071, 4,695,241 and 4,800,116, and the disclosures of those references are hereby incorporated by reference.